Basic vector operations over the rational numbers.
m.r is the rationals used by momentum
var m = require('momentum'); m() === m.r(1); // true
while in the case of rationals it made sense to keep direct equality between the created objects, I think this is not the case with momentumi. However this might change some time in the future.
Another issue is that no matter how much I wish, there isn't a good, widely supported way to subclass array (not until es6 is widely supported). The workarounds available kinda create more problems than they solve, so after a day of thinking I went in the minimalist direction. This also means, that while momentum methods expect arrays and scalars with add, sub, scale, disperse, dot methods on them, the module's user should provide these methods.
Probably worth to mention that the API gives you easy solution to this:
var m = require('momentum'); var equal = require('deep-equal'); var r = m.r; equal(m.disperse(m([1,4,7,9,16]), r(12)), m([r(1,12),r(1,3),r(7,12),r(3,4),r(4,3)])); // true
all methods on momentum objects will return an array of rationals
with the exception of
.dot, which will return a single rational
Casting an array of integers to rationals
m().toString() // 3/1
Casting an integer to a rational
m.r(5).toString() // 5/1
m.scale(m([1,3,5]), m.r(7)) // [7/1,21/1,35/1]
m.disperse(m([1,3,5]), m.r(9)) // [1/9,1/3,5/9]
m.add(m([1,3,5]), m([2,4,6])) // [3/1,7/1,11/1]
m.sub(m([3,7,11]), m([2,4,6])) // [1/1,3/1,5/1]
m.dot(m([1,3,5]), m([7,11,13])) // 105/1
m.cross(m([1,3,5]), m([7,11,13])) // [-16/1, 22/1, -10/1]
npm install momentum
You can use it in the browser with browserify